1. Field of the Invention
The present invention relates to a manual control apparatus provided on a zoom lens barrel for an auto focus type camera to allow manual focusing and zooming control.
2. Description of the Related Art
Generally, an auto focus type camera has a motor for moving back and forth a group of photographic lenses in the direction of the optical axis thereof, wherein automatic focusing is performed by controlling rotation of the motor in accordance with the range of distance from an object. Manual focusing is, however, required in some circumstances. To meet such a requirement, therefore, a manual control ring is also provided on the lens barrel of a camera, so that rotational operation of the control ring moves the photographic lenses in the direction of the optical axis thereof, whereby manual focusing is enabled.
With a zoom lens barrel, in addition to the manual control ring, a zoom control ring is provided for controlling zooming by hand.
In such a device, since it is connected to the photographic lenses at all times, a manual focusing control ring is also made to rotate together with the lenses when the auto focus starts to operate. Consequently, if the user's hand is touching the manual control ring at that time, the motor and intermediary connecting members have a tremendous load imposed thereon, which disadvantageously causes failure and malfunction in focusing. In most cases, in order to avoid this, the manual control ring is disposed at such a position that it is most unlikely that the ring will be carelessly touched by the hand. But this results in another disadvantage in that manual control of the ring is very difficult when it is needed.
Also with an interchangeable lens having a long lens barrel such as a telephoto lens, a member for covering a manual control ring is often provided so as to avoid careless touching of the ring by the hand. With a device of this type, however, the member must be separately provided and be made longer and larger than the control ring, which needs to be a certain length from the viewpoint of controllability of the ring when it needs to be manually controlled. This means that the lens barrel must be made larger, which makes it difficult to take photos while the camera is being held by the hand. In addition, since the motor is forced to rotate the large manual control ring during automatic focusing operation, it has an enormous load imposed thereon, which results in a further disadvantage in that a remarkable reduction of the life of the motor is caused by this.